During any operation wherein a plasma is contained in a vacuum vessel, there is always a possibility that contaminants will collect in the vessel and degrade the vacuum properties, necessitating removal before operation of the vacuum vessel can be continued. For instance, in plasma arc systems or in plasma centrifuges where ions of a rotating plasma are separated in; chamber by centrifugal forces according to their masses, at least some of to plasma's ions will be driven into the chamber wall as the plasma transits the system. If so, they can collect on the chamber wall and thereby contaminate the chamber. Even for applications wherein ion collisions with the chamber wall are desired, they will still eventually contaminate the chamber and must be removed. In other systems wherein ions and neutrals of a plasma are used for deposition or etching of a substrate, such as may be required for the manufacture of semi-conductor wafers, the contamination problem also exists. For example, a device such as disclosed in U.S. application Ser. No. 08/690,149 for an invention entitled "Device and Method For Processing a Plasma to Alter the Surface of a Substrate," envisions the generation of contaminated particles which will collect on the walls of the vacuum chamber. In these, and in many other examples where vacuum chambers and process vessels are used to contain plasmas for a variety of purposes, the contaminants which are generated must somehow be removed from the vessel chamber in order to clean the vessel.
Heretofore, the removal of contaminants from a vacuum chamber has typically been a lengthy and involved process. Specifically, in order to clean a vacuum vessel chamber, it has been necessary to completely shut down the operation of the vacuum vessel. This has involved completely ceasing the operation, removing the plasma from the chamber, and compromising the vacuum in the vessel. Once all of this has been done, the vessel walls can then be either chemically or mechanically cleaned. Then, after the vessel walls have been properly cleaned, the vacuum in the vessel must be reestablished before a plasma can again be generated in the vacuum vessel. Not surprisingly, all of this can be expensive and time consuming.
In light of the above, it is an object of the present invention to provide a system and method for removing plasma contaminants from a vacuum vessel which can be accomplished without compromising the vacuum in the vacuum vessel. Another object of the present invention is to provide a system and method for removing deposited contaminants from the wall of a plasma centrifuge or plasma arc system which can be accomplished during the continued operation of the system. Still another object of the present invention is to provide a system and method for removing plasma contaminants from a vacuum vessel which is conceptually easy to operate, relatively simple to manufacture and comparatively cost effective.